In view of ever-growing energy conservation and environmental concerns, fluorescent lighting fixtures are becoming the first choice for many commercial and residential lighting applications. In many commercial lighting applications where a long-life, high-output light is desired the choice is often a fixture using a high-intensity-discharge (HID), metal halide or high-pressure sodium (HPS) lamp. However, such lamps tend to exhibit high glare, heat generation, unnatural shades of light, and other inefficiencies that render them a good, but not an optimal choice for lighting large commercial spaces. FIG. 1 shows an example of an HID fixture 100 mounted from a garage ceiling beam 102. This example includes a single HID lamp 104 (shown in phantom) surrounded by a metallic or sturdy plastic reflector 106. The reflector may be covered with transparent plate (not shown) to seal it or other wise protected from debris (using a grating, for example). The lamp generates a downward light as shown. In this model, a transparent annulus 110 also generates a sideways lighting effect (dashed arrows 112. This provides a fuller lighting effect in a low-ceiling environment, as described further below.
One example of a large open space requiring commercial lighting is an indoor parking garage structure. In such structures lights may be operating continuously and excess heat may be problematic in underground, enclosed parking areas. Fluorescent lights present a desirable alternative in terms of their white, broad-spectrum output, cool operation and high energy efficiency. However, fluorescent lamps may exhibit lower overall light output (measured in lumens) than comparable high-intensity commercial lamps. For example, half their light is directed opposite the intended target of illumination, requiring a reflector to return this light to the target. Fluorescent lamps are also provided in long tubes that may pose challenges in focusing and distributing their light.
In most parking garage spaces, the ceiling height may be relatively low (for example, 8-12-foot ceiling height). Thus, fixtures that throw substantial quantities of horizontally directed light are desirable so as to avoid a spotting effect. This is an advantage with high-intensity lamps, which can be directed to throw substantial light sideways, as well as downward. In addition, traditional high-intensity fixtures for outdoor and parking area-placement are weatherproof, having durable sealed covers that keep moisture, vapor and other contaminants away from their internal wiring and components. However, fluorescent fixtures are typically open to the elements-many being fitted with an unsealed diffuser cover.
It is, thus, highly desirable to provide a lighting fixture that uses fluorescent tubular lamps, or another type of elongated light source, such as an LED array/strip. This elongated lighting fixture should be particularly suitable for parking areas and other enclosed structures, and afford superior light distribution (photometrics) and overall performance. Such a fixture should be easily retrofit into existing structures and exhibit performance generally similar to other high-intensity fixture types with generally lower power consumption. This fixture should be able to provide desired output using as few as two conventional fluorescent lamps or other elongated lighting sources. It should also be mountable in a pendant manner with a sealed housing to keep out moisture and contaminants.